The present invention relates to a liquid ejecting apparatus and a method for maintaining and recovering ejection performance of the apparatus and, more particularly, to an ink-jet printing apparatus which performs printing by ejecting liquid droplets (ink droplets) onto a printing medium, and a method for recovering ejection performance of the apparatus.
Conventionally, a liquid ejecting apparatus such as an ink-jet printer is widely researched and developed, and has became popular as a consumer equipment.
In ink-jet printers, for example, the viscosity of ink increases upon evaporation of a solvent of ink from orifices (nozzles), and the ejection performance may deteriorate. In order to prevent this, many ink-jet printers are equipped with recovering means including pressurizing or suction means for forcibly discharging ink from the nozzle.
In recent years, a demand for higher recording speed is increased. In order to meet the demand, the number of nozzles and ink-jet printheads which are supplied the same kind of ink tend to increase.
However, if the number of nozzles or ink-jet printheads which are supplied the same kind of ink is increased, and the recover means is constructed to discharge ink from all the nozzles, there must be problems that the amount of ink consumed in recover processing increases, and hence the running cost increases.
To solve this problem, the nozzles may be divide into a several groups and recover processing may be performed in groups having nozzles for which ink discharge should be performed.
However, there must be a case that the number of groups which need recover processing is different every time the recover processing is performed, and hence the number of groups for performing the recover processing at the same time is different whenever the recover processing is performed, and a case that the number of groups for performing the recover processing at the same time is the same but the number of nozzles in the groups is different, and hence the number of nozzles for performing the recover processing at the same time is different whenever the recover processing is performed. In such a case, if the recover processing is always performed in the same way, an amount of ink discharged from one nozzle may be different whenever the recover processing is performed, since the same kind of ink is reserved in the same ink reservoir means. This causes a problem that ink may not be discharged from each nozzles in the amount required for recover processing, or an excessive amount of ink is discharged from nozzles.
It is an object of the present invention to provide a liquid ejecting apparatus which can recover ejection performance of each of liquid ejection openings by discharging a necessary amount of liquid from each ejection openings, and can reduce the amount of liquid consumed by the recover processing, if the number of ejection openings for performing the recover processing at the same time varies.
It is another object of the present invention to provide a method for maintaining and recovering ejection performance of a liquid ejecting apparatus which can recover ejection performance of each of liquid ejection openings by discharging a necessary amount of liquid from each ejection openings, and can reduce the amount of liquid consumed by the recover processing, if the number of ejection openings for performing the recover processing at the same time varies.
According to the present invention, the above object is attained by a liquid ejecting apparatus comprising:
a plurality of liquid ejection openings to which liquid reserved in the same liquid reservoir means is supplied;
ejection performance maintaining and recovering means for forcibly discharging the liquid from liquid ejection openings selected from the plurality of liquid ejection openings; and
control means for controlling the ejection performance maintaining and recovering means in accordance with number of selected liquid ejection openings so as to substantially equalize an amount of ink discharged from each of the liquid ejection openings, regardless of the number of selected liquid ejection openings.
According to the present invention, another object is attained by a method for maintaining and recovering ejection performance of an apparatus having
a plurality of liquid ejection openings to which liquid reserved in the same liquid reservoir means is supplied, said method comprising the steps of:
ejection performance maintaining and recovering step for performing ejection performance maintaining and recovering operation which forcibly discharges the liquid from liquid ejection openings selected from the plurality of liquid ejection openings; and
control step for controlling the ejection performance maintaining and recovering operation in accordance with number of selected liquid ejection openings so as to substantially equalize an amount of ink discharged from each of the liquid ejection openings, regardless of the number of selected liquid ejection openings.
That is, in the present invention, in an apparatus having a plurality of liquid ejection openings to which liquid reserved in the same liquid reservoir means is supplied, ejection performance maintaining and recovering operation which forcibly discharges the liquid from liquid ejection openings selected from the plurality of liquid ejection openings is performed, and the ejection performance maintaining and recovering operation is controlled in accordance with number of selected liquid ejection openings so as to substantially equalize an amount of ink discharged from each of the liquid ejection openings during the ejection performance maintaining and recovering operation, regardless of the number of selected liquid ejection openings.
According to the above arrangement, in the ejection performance maintaining and recovering operation performed for a plurality of liquid ejection openings to which liquid reserved in the same liquid reservoir means is supplied, even if the number of liquid ejection openings for which the maintaining and recovering operation is to be simultaneously executed increases, a necessary amount of liquid required for maintaining and recovering the ejection performance can be discharged from each liquid ejection openings. And even if the number of liquid ejection openings for which the maintaining and recovering operation is to be simultaneously executed decreases, the amount of liquid consumed in the maintaining and recovering operation is reduced, since the liquid is discharged no more than the necessary amount required for maintaining and recovering the ejection performance.
Therefore, the number of liquid ejection openings for which recovering operation is to be simultaneously executed changes, the original performance of the liquid ejecting apparatus can be maintained by discharging liquid in an amount large enough to recover the ejection performance from each liquid ejection openings. In addition, the running cost of the liquid ejecting apparatus can be reduced by decreasing the amount of liquid consumed for the maintaining and recovering operation.
Note that the ejection performance maintaining and recovering means may have an arrangement which includes a negative pressure generating means and forcibly discharges liquid from the selected liquid ejection openings with the negative pressure generated by the negative pressure generating means or an arrangement which includes a pressure generating means and forcibly discharges liquid from the selected liquid ejection openings with the pressure generated by the pressure generating means.
If the plurality of liquid ejection openings are divided into a plurality of liquid ejection opening groups each having a same number of liquid ejection openings, the ejection performance maintaining and recovering means is preferably configured to forcibly discharge the liquid from liquid ejection openings belonging to liquid ejection opening groups selected from the plurality of liquid ejection opening groups, and the control means is preferably configured to control the ejection performance maintaining and recovering means in accordance with number of selected liquid ejection opening groups so as to substantially equalize an amount of ink discharged from each of the liquid ejection openings by the ejection performance maintaining and recovering operation.
If the plurality of liquid ejection opening groups each having a same number of liquid ejection openings are provided on respective liquid ejecting heads, the ejection performance maintaining and recovering means is preferably configured to forcibly discharge the liquid from liquid ejection openings belonging to liquid ejecting heads selected from the plurality of liquid ejecting heads, and the control means is preferably configured to control the ejection performance maintaining and recovering means in accordance with number of selected liquid ejecting heads so as to substantially equalize an amount of ink discharged from each of the liquid ejection openings by the ejection performance maintaining and recovering operation.
It is preferable that the apparatus further comprise a detection means for detecting a liquid ejection opening that requires the ejection performance maintaining and recovering operation.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.